How to set KeepAlive for TCP connections

[PragmaTwice]

I found that Tcp(usize) in enum KeepAlive has been removed since about 2019.
Because I am using websocket, the option Timeout(usize) in KeepAlive is useless.
How to use SO_KEEPALIVE for TCP connections in actix-web now?

[robjtede]

So you can delegate to the OS keepalives with https://docs.rs/actix-http/2.2.0/actix_http/enum.KeepAlive.html. Otherwise you'll need to use socket2 to create a socket that has the exact duration set up and pass it to HttpServer::listen.